FRP flange selection is the step where a fiberglass or GRE line either mates cleanly to a steel valve, pump or manifold — or fails the first bolt-up. This guide is for operators, EPC teams and procurement engineers who already know they need a fiberglass flange (also called a GRP flange or GRE flange) and who need a clean way to match that flange to the pipe system, declare the steel interface, and put comparable fields into the RFQ.
It is a flange product selection and RFQ guide, not a joint-taxonomy page. Bell-and-spigot versus threaded versus flanged joints belong in Bell-and-Spigot vs Threaded vs Flanged Joints on FRP/GRE Oilfield Pipe. Elbows, tees, reducers and couplings belong in FRP and GRE Pipe Fittings: Elbows, Tees, Reducers and Couplings Matched to the Pipe System. Here the job is narrower: choose the flange, lock the steel-side interface, and ask for the manufacturer procedure before torque becomes a field argument.
Where FRP/GRE flanges are used
Start from the services the catalogue lists, not from a marketing headline. The CNPS catalogue page Reliable FRP Flanges for Industrial Piping Systems frames FRP flanges for industrial piping and states they are highly suitable for chemical, marine and water-treatment systems. The same page states they are widely used in seawater desalination plants, chemical processing, marine pipelines and wastewater systems.
On a typical oilfield or industrial route that means:
- pipe-to-valve and pipe-to-pump tie-ins where the other side is steel;
- steel manifold, skid or vessel nozzles that must accept a fiberglass line;
- inspectable flanged breaks on chemical, water or marine GRE/FRP runs;
- blind ends and temporary closures where a frp flange cover or blind flange is specified.
That list is a service map, not a qualification. A flange that sits on one of those duties still needs a declared pipe standard, class, size and steel interface before offers can be compared. For the broader GRE pipes-and-fittings family on www, the product page is GRE Pipes And Fittings With NSF/ANSI/CAN 61 — the only www fittings product page today. NSF/ANSI/CAN 61 appears in that page title; this guide does not treat the string as a certification claim.
CNPS supplies API 15HR and API 15LR certified fiberglass pipe. That statement names the pipe family the flange must match; it does not invent a flange rating, drilling standard or gasket type.
Matching the flange to the pipe system
The flange is part of the pipe system, not a free-standing hardware SKU. Match it to the same standard family and class as the line it sits on:
- API 15HR lines. How to read an API 15HR claim and which evidence to request is covered in API 15HR Fiberglass Line Pipe Standard: Reading an API 15HR Claim and the Evidence to Request. When the line is already on a high-pressure GRE shortlist, use High-Pressure Fiberglass Line Pipe Selection: When API 15HR GRE Fits (Service Envelope, DN, Joints, RFQ) for the pipe envelope, then bring the flange along at the same class.
- API 15LR lines. Where low-pressure fiberglass fits, and which ordering and inspection fields to declare, is covered in API 15LR Low-Pressure Fiberglass Pipe and Fittings: Where 15LR Fits, Ordering Fields and Inspection Witness Points. Do not put a high-pressure flange assumption onto a 15LR run — or the reverse — without stating the class in the RFQ.
Same class means the same pressure class language the pipe offer uses, the same joint family at the flange stub if the pipe end is flanged, and the same resin / temperature basis you expect the datasheet to use. Do not assume a steel flange class can ride onto a GRE line unchanged, and do not assume a catalogue flange headline replaces the size-specific datasheet.
Steel interface fields: drilling, face, gasket and bolting
Most FRP/GRE flange failures in the field are interface mismatches, not mysterious material problems. The CNPS catalogue FAQ states that an FRP flange can be connected to standard metal pipeline systems using appropriate gaskets and bolts. It does not publish a drilling standard, face type, gasket material or bolt torque. Those are RFQ-declared fields.
Write them before you ask for a quotation:
| Interface field | What you declare | Why it stays in the RFQ |
|---|---|---|
| Drilling / bolt pattern | The steel-side standard the valve, pump or nozzle already uses | Catalogue pages do not publish a bolt-circle table for FRP flanges |
| Face type | The facing the mating steel flange expects | Face type is not stated on the CNPS flange catalogue page |
| Gasket | Material, thickness and facing match for the medium and temperature | “Appropriate gaskets” is stated; the gasket itself is not specified |
| Bolting | Bolt grade/size set, lubricant and make-up sequence you will accept | Bolt-up belongs to the manufacturer procedure, not to a blog table |
| Class language | The pressure-class wording used on the pipe offer and the steel side | No ASME class numbers are stated for CNPS FRP flanges on the catalogue page |
If the steel side is already installed, copy its datasheet into the RFQ rather than asking the flange maker to guess. If both sides are new, pick one governing steel standard and state it once for the whole joint.
Temperature window versus design temperature
The CNPS FRP flange catalogue states a temperature range of −40 °C to 110 °C. That is the published window, not the design temperature of your line. Your RFQ still needs:
- design fluid temperature and design ambient;
- any short-term excursion or steam-out you expect;
- the temperature basis you want the flange datasheet to use (same basis as the pipe);
- confirmation that the gasket and bolting you named stay inside that window.
Stay inside the published −40 to 110 °C band, then ask for the size-specific rating at your design temperature. Do not treat the catalogue window as a qualified rating for every diameter and every resin system.
Flange covers and blind flanges
Not every “flange” on a GRE/FRP BOM is a through-flow connection. Procurement often needs:
- Stub-end / stub-style flanges that terminate a fiberglass pipe into a bolted joint;
- Blind flanges that close a run for hydrotest, isolation or future tie-in;
- Flange covers (the frp flange cover intent) that protect an open flange face during shipping, storage or staged construction.
Treat covers and blinds as tagged scope, not as free accessories. State quantity, size, facing match and whether the cover is temporary or a rated blind. The catalogue notes that standard accessories are available; it does not publish a cover or blind SKU list — so the BOM line is still yours to write.
Installation and torque: ask for the manufacturer procedure
Composite flanges do not forgive steel habits. Bolt-up sequence, cross-pattern, lubricant, target load and re-torque after settle all belong in the manufacturer procedure for the offered flange — not in a generic steel torque chart copied into the RFQ.
Ask for, and keep with the offer:
- the written make-up / bolt-up procedure for the offered flange size and facing;
- any hold points for gasket seating and re-check after pressure test;
- who is responsible for field supervision if the joint is made at site;
- storage and handling notes for faces and covers before installation.
This guide does not publish torque values. If a quotation arrives without a procedure, treat that as an incomplete offer.
Flange RFQ fields
Put the flange on the same RFQ sheet as the pipe and fittings, with one tag per joint:
| RFQ field | What to write |
|---|---|
| Tag / line | P&ID or isometric tag for the joint |
| Pipe standard / class | API 15HR or API 15LR (or other declared family) and the class language of the pipe offer |
| Size | DN / NPS of the pipe end and of the mating steel flange |
| Flange role | Stub / through / blind / cover |
| Steel interface | Drilling pattern, face type, gasket, bolting — as declared above |
| Design temperature | Value inside the published −40 to 110 °C catalogue window, plus basis |
| Medium | Fluid, including corrosives and cleaning chemicals |
| Documents | Datasheet per size, make-up procedure, and any certificate copies you require for the matching pipe family |
For a China FRP flange manufacturer enquiry, send the completed fields rather than a one-line “FRP flange” request — comparable offers need the steel interface and pipe class on day one. When the sheet is filled in, send it through Talk to an Engineer so the offer is built against your tags, not a generic catalogue headline.
FAQ
What is FRP flange selection in this guide?
It is the work of matching a fiberglass or GRE flange to the pipe standard and class, declaring the steel-side drilling, face, gasket and bolting, and locking those fields in the RFQ before offers are compared. It is not a joint-type taxonomy and not a fittings catalogue rewrite.
Can an FRP flange mate to a steel valve?
The CNPS catalogue FAQ states that an FRP flange can be connected to standard metal pipeline systems using appropriate gaskets and bolts. You still declare the steel drilling, face and gasket; those details are not published as a fixed table on the catalogue page.
Do I need a different flange for API 15HR and API 15LR pipe?
Declare the same standard family and class as the pipe. High-pressure and low-pressure fiberglass lines are not interchangeable by default — match the flange to the line you actually ordered, and keep the pipe guides linked above as the owners of those decisions.
What temperature window does CNPS list for FRP flanges?
The catalogue page states −40 °C to 110 °C. Your design temperature must sit inside that window, and the datasheet must speak to your size and temperature basis.
What should I ask for when I need an FRP flange cover?
Tag it as a cover or blind, state size and facing match, say whether it is temporary protection or a rated blind, and include quantity on the BOM. Do not assume “accessories available” means a free cover on every flange.
Where do bolt torque values come from?
From the manufacturer procedure for the offered flange — requested in the RFQ. This guide does not invent torque numbers, ASME class ratings or drilling patterns.
What is the fastest next step?
Browse the flange range on the global catalogue linked above, use the www GRE pipes-and-fittings product page as the single product CTA, fill the RFQ table, and send it through Talk to an Engineer.
